The present invention relates to a blood collecting apparatus.
Blood collecting apparatuses, such as that disclosed in Japanese Patent Publication No. 3153/1976, have been proposed. Conventional blood collecting apparatuses are such that a blood bag is accommodated in a blood collecting chamber, a limit switch detects that the thickness of the blood bag, expanding as blood collection proceeds, has reached a predetermined level, and the blood collecting action is stopped on the basis of this detection, so that a predetermined volume of blood is collected and secured in the blood bag.
Conventional blood collecting apparatuses are also such that a plate supporting the blood bag is swung during the collection of blood into the blood bag, thereby causing blood to be stirred together with an anticoagulant, such as CPD solution (Citrate-Phosphate-Dexture) already charged in the blood bag.
Since it is difficult to accurately measure the amount of collected blood by measuring a change in the thickness of the blood bag, one may consider that, in order to measure the amount of collected blood more accurately, the collected blood amount may be measured by measuring a change in the weight of the blood bag during blood collection.
However, in the case where, during blood collection, a change in the thickness of the blood bag is measured while the blood bag is being vibrated, the exterior configuration of the bag changes as the blood within the blood bag is shaken by the vibration. Accordingly, the thickness of the bag changes not only with changes in the amount of blood collected but also with changes in the angular position of the vibration. For this reason, in order to effect accurate measurement, it is necesssary for the blood bag to be held in its motionless state, and then have its thickness measured at least at the blood collection terminating stage at which the set amount of blood to be collected must be finally reached by the amount of blood collected.
In the case where, during blood collection, a change in the weight of the blood bag is measured while the blood bag is being vibrated, the state in which the weight of the bag applies load on the weight measurement device changes with changes in the angular position of the vibration, thereby making it impossible to perform stable measurement of weight. Also in this case, therefore, in order to effect accurate measurement, it is necessary for the blood bag to be held in its motionless state, and then have its weight measured at least at the blood collection terminating stage at which the set blood collection amount must be finally reached by the amount of collected blood.
Thus, both in the case where the amount of collected blood is measured by detecting a change in the thickness of the blood bag, and in the case where the amount of collected blood is measured on the basis of a change in the weight of the blood bag, it is necessary, at least at the blood collection terminating stage, to effect the measurement of the amount of collected blood while the blood bag is held in its stoppage state. Specifically, when the amount of collected blood has reached a certain amount (hereinafter referred to as "vibration stopping reference amount") at a certain stage before it reaches a set amount of blood to be collected, the vibration of the blood bag is made to remain stopped. The thickness or weight of the blood bag is measured in this stoppage condition.
However, the speed at which blood is collected into the blood bag varies between individual donors. This explains the occurrence of the following cases. When the vibration stopping reference amount is set at a certain value (e.g., when the vibration stopping reference amount is 30 ml while the set amount of blood to be collected is 200 ml), if the donor allows only a low blood collecting speed, the yet-to-be-collected blood collecting time required after the stoppage of blood collection may be as much as several minutes, whereas if the donor allows a high blood collecting speed, the yet-to-be-collected blood collecting time required after the stoppage of blood collection ranges from several seconds to several tens of seconds. In the first case, blood is collected into the blood bag from a donor allowing only a low blood collecting speed, and the blood collection continues in the condition where the vibration of the blood bag remains stopped for a long time. This means that the blood collected is not adequately mixed with an anticoagulant, resulting in the risk of blood coagulation being involved.
The object of the present invention is to provide accurate measurement of blood collected into a blood container, and also to positively prevent of coagulation of collected blood.